It's interesting to think about ways in which using Groupon would be beneficial.

Maybe for a new entrant to a geographic market where they are willing to settle with much lower margins? So you would in that case use Groupon to get your initial customers at the expense of neighboring competitors. And by keeping prices permanently low you would potentially keep those customers.

Presumably, if you can keep that up and competitors cannot compete, you could drive them out of business and then raise prices. Sort of a Walmart 2.0 strategy.